The invention relates generally to welding systems, and more particularly to improved techniques for effective control of welding arcs through digital control and coordination of system components.
A number of welding systems and processes have been developed and are currently in use. In general, these involve creation of an arc between an electrode and a work piece, which serves to melt filler metal and the work piece. These refuse to establish the desired joint. In some processes, such as gas metal arc welding (GMAW), a subset of which is commonly called metal inert gas (MIG) welding, flux-cored arc welding (FCAW), and shielded metal arc welding (SMAW), commonly called “stick” welding, the electrode itself is melted and becomes part of the weld. In other processes, such as gas tungsten arc welding (GTAW), commonly called tungsten inert gas (TIG), an electrode is not melted, but serves only to sustain an arc that melts the work piece and separate adder metal, when used.
In all of these welding processes, power supplies are used, along with other components, the construction and operation of which may vary based upon the type of process, and the way it is carried out. For example, in MIG systems, a power supply is generally coupled to a wire feeder that provides a controlled supply of welding wire electrode through a welding gun. The power supply or wire feeder is also typically coupled to a supply of shielding gas. In both MIG and TIG systems, moreover, the power us ultimately supplied to a welding gun or torch, used to complete the electrical circuit for the welding arc.
Control of such welding systems is typically based on feedback of various measured parameters, with open loop control of others. For example, currents and/or voltages are often measured, and used as a basis for closed loop control of pulses, output power levels, and so forth, as dictated by the particular welding regime selected. Other settings, such as wire feed speeds, may be essentially open loop, although there, too, tachometer readings, motor drive voltages, and similar parameters may be sensed and/or controlled in closed loop manners.
Conventional control schemes of this type, while very effective in providing high quality welds, are subject to certain drawbacks. In particular, the reliance of feedback for much of the process control makes the systems inherently reactive, resulting in delays that simply cannot be avoided due to the nature of the communication and control approach. Only limited improvements can be made, such as through faster signal transfer, higher processing speeds, and so forth, although these too have inherent limits.
There is a need, therefore, for improved techniques for control of welding processes that can reduce delays and improve the welding operations.